As per http://www.hemphasis.net/History/harriedhemp.htm Kentucky farmers grew hemp used mainly for rope in the marine industry. "Kentucky first planted hemp near Danville in 1775. In 1790, hemp fiber was first advertised for sale in local papers. The hemp industry rapidly expanded and Kentucky became the industry center for the next 100 years. Most of Kentucky's hemp was grown in the "bluegrass" region that includes Fayette, Woodford, Jessamine, Garrard, Clark, Bourbon, Boyle, Scott and Shelby counties. In 1811, there were almost 60 ropewalks in Kentucky, and by the late 1850's, more than one-third of the 400 bagging, bale rope and cordage factories in America were located there." One would surmise limestone and weather among other factors gave the Bluegrass State it's comparative advantage. Maybe, in the future, water-retting hemp will be the norm.
Again, from the link above: "Despite the prevailing knowledge that water-retted hemp was better suited for naval cordage and the fact that it generally drew a higher price on the market than dew retted hemp, few American hemp farmers adopted the practice. As late as 1913, Dewey noted that "dew retting is practiced almost exclusively". While a higher price could be received for water-retted hemp, there was a limited market for it. For American farmers of that time, there was a bigger market for dew retted hemp."
This pdf also has some great info about hemp production: http://www.globalhemp.com/wp-content/uploads/2000/01/ages001Ee.pdf.
Hempseed Oil
The benefits of hemp oil are explained here: http://www.reuters.com/article/2014/02/11/us-hempseed-oil-study-idUSBREA1A1XS20140211
"The researchers examined the fatty acid profile of hempseed oil and found that polyunsaturated fatty acids (PUFAs) made up about 75 percent of the oil. PUFAs include omega-6 and omega-3, the fatty acids found in some meats as well as flax and fish oils.
The high amounts of one omega-3 fatty acid, alpha linolenic acid, "may have favorable nutritional implications and beneficial physiological effects on the prevention of coronary heart disease and cancer," the authors write."
Also, "With an ideal ratio of omega-6 and -3 fatty acids and some plant chemicals thought to lower high blood pressure, hempseed oil has potential as part of a heart-healthy diet..."